Question

Use the data in the table above to calculate an approximate ΔH∘ in kilojoules for the synthesis of hydrazine from ammonia:

2NH3(g)+Cl2(g)⟶N2H4(g)+2HCl(g)

Answer 1

On the left (reactant) side you have 6 N-H bonds and 1 Cl-Cl bond
On the right (product) side you have 4 N-H bonds, 1 N-N bond and 2 H-Cl bonds

Add up the bond energies for each side (multiplying by the number of bonds) and calculate the difference for your ΔHº